1. Field of the Invention
The present invention relates to a tetrafluoroethylene-perfluorovinylether copolymer, and more particularly to a tetrafluoroethylene-perfluorovinylether copolymer capable of forming a film or sheet having a good resistance to flex fatigue by molding.
2. Description of the Prior Art
Various tetrafluoroethylene-perfluoro(lower alkyl vinyl ether) copolymers are well known, and most of them relate to copolymers of perfluoro(methyl vinyl ether) or perfluoro(propyl vinyl ether) and tetrafluoroethylene. No extensive studies of tetrafluoroethylene-perfluoro(ethyl vinyl ether) copolymer have been made yet. It is also said that the so far obtained tetrafluoroethylene-perfluoro(ethyl vinyl ether) coplymers are brittle and are not suitable for formation of films or sheets.